In-plane behavior of perforated brick masonry walls

This paper reports the results of experimental and theoretical research conducted on perforated brick masonry walls under in-plane loading. The walls?? structural behavior depends strongly on their specific features, e.g. geometry, mechanical properties of the masonry material, brick arrangement and loading conditions. The experimental program was designed to study the incidence of brick arrangement in the spandrels and piers, and of the acting vertical load on the failure mode and load-bearing capacity of the walls. Six specimens of brick masonry wall with a central opening were submitted to a constant vertical load and a monotonic horizontal force that was gradually increased until the kinematic mechanism condition was reached. The object of the theoretical research was to develop a simplified analytical model for describing the kinematic mechanism of the walls. The results of the experiments indicate that brick arrangement strongly influences the failure mode and load-bearing capacity of the walls. Proper a priori assessment of the failure mode of walls becomes fundamental to an accurate evaluation of their load-bearing capacity using the proposed model.     

Direct determination of rare earth elements at the subpicogram per gram level in antarctic ice by ICP-SFMS using a desolvation system

A method, based on inductively coupled plasma sector field mass spectrometry coupled with a microflow nebulizer and a desolvation system, has been developed for the direct determination of rare earth elements (REE) (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) down to the subpicogram per gram level (1 pg/g = 10(-12) g g(-1)) in approximately 1 mL of molten Antarctic ice. Contamination problems were carefully taken into account by adopting ultraclean procedures during the sample pretreatment phases. The use of a desolvation system for sample introduction during the analysis greatly reduced spectral interferences from oxide formation; the residual interfering contributions were calculated and subtracted whenever necessary. A matched calibration curve method was used for the quantification of the analytes. Instrumental detection limits ranged from 0.001 pg/g for Ho, Tm, and Lu to 0.03 pg/g for Gd. The precision, in terms of relative standard deviation on 10 replicates, ranged from 2% for La, Ce, Pr, and Lu, up to 10% for Er, Tm, and Yb. This methodology allowed the direct determination of REE in a 1-mL sample of ancient Antarctic ice with concentration ranges between 0.006 and 0.4 pg/g for Tm and 0.9-60 pg/g for Ce.     

Influence of the side functionalization of quinquethiophene-S,S-dioxides on the morphology of blends with poly(3-hexylthiophene): scanning force microscopy reveals

Blends of an electron donor, i.e. a regioregular poly(3-hexylthiophene) (P3HT), with electron acceptors, a series of soluble quinquethiophene-S,S-dioxides (T5Os) bearing different alkyl side groups were self-assembled at surfaces. Scanning Force Microscopy (SFM) studies revealed that while the T5O symmetrically functionalized with two hexyl groups in the central thiophene (1) self-organizes into micrometer sized crystals embedded in a grainy matrix of P3HT, by substituting the central thiophene of 1 with one hexyl and one methyl unit (2) smaller and less anisotropic crystals of the acceptor having a sub-micrometer scale size were formed. The generation of these crystals is due to the joint effect of different non-covalent intermolecular interactions between the T5Os that self-segregate from the P3HT. By derivatizing the compound 1 with cyclo-hexyl moieties in the four external thiophenes molecule 3 was obtained. Such system was found to assemble into grainy disordered structures when co-deposited with P3HT, providing evidence for the absence of a phase segregation between the two components. Generally, the self-assembly at surfaces is governed by the interplay of intramolecular as well as intermolecular and interfacial interactions. In the present case, the cyclo-hexyl side groups in 3 both induce an intramolecular loss of planarity of the thiophene rings and hinders intermolecular interactions, reducing the tendency of the molecules to self-associate forming large crystals, whereas the symmetrical functionalization of the two central thiophenes with hexyl chains favours the crystallization of the T5O. The reported results demonstrate that subtle differences in the chemical functionalization can lead to different types of molecular architectures at surfaces. This is of importance since controlling the self-organization of pi-conjugated molecules at surfaces towards pre-programmed assemblies is a viable approach to enhance their electronic and luminescent properties, which should help to improve the performance of organic devices.     

Conventional and novel processing methods for cellular ceramics

Cellular ceramics are a class of highly porous materials that covers a wide range of structures, such as foams, honeycombs, interconnected rods, interconnected fibres, interconnected hollow spheres. Recently, there has been a surge of activity in this field, because these innovative materials have started to be used as components in special and advanced engineering applications. These include filtering liquids and particles in gas streams, porous burners, biomedical devices, lightweight load-bearing structures, etc. Improvements in conventional processing methods and the development of innovative fabrication approaches are required because of the increasing specific demands on properties and morphology (cell size, size distribution and interconnection) for these materials, which strictly depend on the application considered. This paper will cover the main fabrication methods for cellular ceramics, focusing primarily on foams, offering some insight into novel fabrication processes and recent developments.     

Efficient light-scattering calculations for aggregates of large spheres

Calculation of the scattering pattern from aggregates of spheres through the T-matrix approach yields high-precision results but at a high-computational cost, especially when the aggregate concerned is large or is composed of large-size spheres. With reference to a specific but representative aggregate, we discuss how and to what extent the computational effort can be reduced but still preserve the qualitative features of the signature of the aggregate concerned.     

Multi-resolution fuzzy clustering approach for image-based particle characterization for particle systems

Online characterization of particles is an important step for maintaining desired product quality in particulate processes. Direct real-time image analysis is a promising method for monitoring particle systems, and is becoming increasingly more attractive due to availability of high speed imaging devices and equally powerful computers. Performing image segmentation (separation of objects (particles) within one image) accurately becomes a key issue in particle image analysis. This paper presents a novel technique based on combining wavelet transform and Fuzzy C-means Clustering (FCM) for particle image segmentation. Through performing wavelet transform on images, the noise and high frequency components of images can be eliminated and the textures and features can be obtained. FCM is then used to divide data into two clusters to separate touching objects. To quantitatively evaluate this method, a case study involving a particle image is investigated. The procedure of selecting optimum wavelet function and decomposition level for this image is presented. ‘Fuzzy range’ is used as a derived feature for segmentation. The number of particles, particle equivalent diameters, and size distribution before and after partition are discussed. The results show that this method is effective and reliable.     

Designer magnetoplasmonics with nickel nanoferromagnets

We introduce a new perspective on magnetoplasmonics in nickel nanoferromagnets by exploiting the phase tunability of the optical polarizability due to localized surface plasmons and simultaneous magneto-optical activity. We demonstrate how the concerted action of nanoplasmonics and magnetization can manipulate the sign of rotation of the reflected light's polarization (i.e., to produce Kerr rotation reversal) in ferromagnetic nanomaterials and, further, how this effect can be dynamically controlled and employed to devise conceptually new schemes for biochemosensing.     

Mesoporous silicon particles as a multistage delivery system for imaging and therapeutic applications

Many nanosized particulate systems are being developed as intravascular carriers to increase the levels of therapeutic agents delivered to targets, with the fewest side effects. The surface of these carriers is often functionalized with biological recognition molecules for specific, targeted delivery. However, there are a series of biological barriers in the body that prevent these carriers from localizing at their targets at sufficiently high therapeutic concentrations. Here we show a multistage delivery system that can carry, release over time and deliver two types of nanoparticles into primary endothelial cells. The multistage delivery system is based on biodegradable and biocompatible mesoporous silicon particles that have well-controlled shapes, sizes and pores. The use of this system is envisioned to open new avenues for avoiding biological barriers and delivering more than one therapeutic agent to the target at a time, in a time-controlled fashion.